1. Field of the Invention
This invention relates generally to the detection of electromagnetic fields, and more particularly to the direct detection of the magnetic vector potential "field" associated with the electromagnetic field.
2. Description of the Related Art
It is known in the related art to utilize a Josephson interferometer, that is, a pair of Josephson devices coupled by two superconducting leads, to detect the presence of a magnetic flux which is applied through the interferometer loop. This class of devices is known as superconducting quantum interference devices or SQUID devices.
It is also known in the prior art that the magnetic fields of ordinary electromagnetic theory can be derived from a magnetic vector potential function. It is also known in the prior art that if a magnetic vector potential A is of form A=A.sub.1 +A.sub.2 where .gradient..times.A.sub.2 =0, than A.sub.2 does not contribute to the formation of the ordinary observable magnetic fields because B=.gradient..times.A. Early literature has discussed whether the A vector potential "field" had any observable physical effect, or if the A potential was merely a useful artifact in performing computations. With the advent of quantum mechanics, the inclusion of both the electric scalar potential and the magnetic vector potential in the Hamiltonian equation of motion for the electron reinforced the recognition that the magnetic vector potential does in fact result in observable physical phenomenon. One observable phenomenon is the generation of so-called supercurrent across a Josephson junction. This effect has made possible the use of the magnetic vector potential as a carrier of information. However, for practical use of the magnetic vector potential "field" as a carrier of information, better more sensitive detection of the magnetic vector potential "field" is desirable.